The　study　of　the　synchronous　characteristics　and　functional　connections　between　the　functional　cortex　and　muscles　of　hand-grasping　movements　is　important　in　basic　research,　clinical　disease　diagnosis　and　rehabilitation　evaluation.　The　electroencephalogram　(EEG)　and　electromyographic　signal　(EMG)　signals　of　15　healthy　participants　were　used　to　analyze　the　corticomuscular　coupling　under　grasping　movements　by　holding　three　different　objects,　namely,　card,　ball,　and　cup　by　using　the　time-frequency　Granger　causality　method　based　on　time-varying　nonlinear　autoregressive　with　exogenous　input　(TV-NARX)　model　and　Coiflets　wavelet　packet　transform.　The　results　show　that　there　is　a　bidirectional　coupling　between　cortex　and　muscles　under　grasping　movement,　and　it　is　mainly　reflected　in　the　beta　and　gamma　frequency　bands,　in　which　there　is　a　statistically　significant　difference　(p　＜　0.05)　among　the　different　grasping　actions　during　the　movement　execution　period　in　the　beta　frequency　band,　and　a　statistically　significant　difference　(p　＜　0.1)　among　the　different　grasping　actions　during　the　movement　preparation　period　in　the　gamma　frequency　band.　The　results　show　that　the　proposed　method　can　effectively　characterize　the　EEG-EMG　synchronization　features　and　functional　connections　in　different　frequency　bands　during　the　movement　preparation　and　execution　phases　in　the　time-frequency　domain,　and　reveal　the　neural　control　mechanism　of　sensorimotor　system　to　control　the　hand-grasping　function　achievement　by　regulating　the　intensity　of　neuronal　synchronization　oscillations.　Copyright　©　2022　Zhu,　Li,　Shi　and　Shi.